Most unlockers disable multiplayer or cause desynchronization (desync) errors. If you play with a legitimate copy and an unlocker, the game will detect mismatched DLC flags and disconnect. You are effectively locked into single-player only.
Base Victoria 2 features a jarring yellow color for Prussia, which was only "fixed" to the traditional grey/blue in subsequent DLC updates. Risks and Legal Considerations Victoria 2 Dlc Unlocker
trick the platform into recognizing DLC as "owned" by modifying internal library files (e.g., steam_api.dll The Victoria 2 Constraint Victoria 2 Victoria 2 Dlc Unlocker